1. Field of the Invention
The present invention is generally directed and a bone anchor used for occipito-cervical fusion, more specifically, to an occipital fixation screw used as a bone anchor provided with tabs to increase surface and contact area to a bone structure.
2. Background
The spine is routinely subject to high loads which cycle during movement, whereby one of the primary concerns of physicians performing spinal implantation surgeries is the risk of screw pull-out. Screw pull-out occurs when the cylindrical portion of the bone which surrounds the inserted screw fails. A bone screw which is implanted perpendicular to the plate is particularly weak because the region of the bone which fails for pull-out to occur is only as large as the outer diameter of the screw. The amount of bone which must fail increases substantially as compared to pairs of screws which are implanted in parallel along the axis that the loading force is applied.
Along the spinal column, there are important internal tissue structures which, because of their proximity to the implant, may be damaged by a dislocated screw. In the cervical spine, the esophagus is located directly in front of the anterior surface of the vertebral body, and therefore, in potential contact with an implanted cervical plate. Breaches of the esophageal wall permit bacterial contamination of the surrounding tissues, including the critical nerves in and around the spinal cord. Such contamination can be fatal.
Thus, it is desirable to provide improved systems for stabilizing the affixation of a bone plate to a bone structure.